Class ConcurrentSkipListSet<E>
- Type Parameters:
E- the type of elements maintained by this set
- All Implemented Interfaces:
Serializable,Cloneable,Iterable<E>,Collection<E>,NavigableSet<E>,SequencedCollection<E>,SequencedSet<E>,Set<E>,SortedSet<E>
NavigableSet implementation based on
a ConcurrentSkipListMap. The elements of the set are kept
sorted according to their natural ordering,
or by a Comparator provided at set creation time, depending
on which constructor is used.
This implementation provides expected average log(n) time
cost for the contains, add, and remove
operations and their variants. Insertion, removal, and access
operations safely execute concurrently by multiple threads.
Iterators and spliterators are weakly consistent.
Ascending ordered views and their iterators are faster than descending ones.
Beware that, unlike in most collections, the size
method is not a constant-time operation. Because of the
asynchronous nature of these sets, determining the current number
of elements requires a traversal of the elements, and so may report
inaccurate results if this collection is modified during traversal.
Bulk operations that add, remove, or examine multiple elements,
such as AbstractCollection.addAll(java.util.Collection<? extends E>), Collection.removeIf(java.util.function.Predicate<? super E>) or Iterable.forEach(java.util.function.Consumer<? super T>),
are not guaranteed to be performed atomically.
For example, a forEach traversal concurrent with an
addAll operation might observe only some of the added elements.
This class and its iterators implement all of the
optional methods of the Set and Iterator
interfaces. Like most other concurrent collection implementations,
this class does not permit the use of null elements,
because null arguments and return values cannot be reliably
distinguished from the absence of elements.
This class is a member of the Java Collections Framework.
- Since:
- 1.6
- See Also:
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Constructor Summary
ConstructorsConstructorDescriptionConstructs a new, empty set that orders its elements according to their natural ordering.ConcurrentSkipListSet(Collection<? extends E> c) Constructs a new set containing the elements in the specified collection, that orders its elements according to their natural ordering.ConcurrentSkipListSet(Comparator<? super E> comparator) Constructs a new, empty set that orders its elements according to the specified comparator.Constructs a new set containing the same elements and using the same ordering as the specified sorted set. -
Method Summary
Modifier and TypeMethodDescriptionbooleanAdds the specified element to this set if it is not already present.voidThrowsUnsupportedOperationException.voidThrowsUnsupportedOperationException.Returns the least element in this set greater than or equal to the given element, ornullif there is no such element.voidclear()Removes all of the elements from this set.clone()Returns a shallow copy of thisConcurrentSkipListSetinstance.Comparator<? super E> Returns the comparator used to order the elements in this set, ornullif this set uses the natural ordering of its elements.booleanReturnstrueif this set contains the specified element.Returns an iterator over the elements in this set in descending order.Returns a reverse order view of the elements contained in this set.booleanCompares the specified object with this set for equality.first()Returns the first (lowest) element currently in this set.Returns the greatest element in this set less than or equal to the given element, ornullif there is no such element.Returns a view of the portion of this set whose elements are strictly less thantoElement.Returns a view of the portion of this set whose elements are less than (or equal to, ifinclusiveis true)toElement.Returns the least element in this set strictly greater than the given element, ornullif there is no such element.booleanisEmpty()Returnstrueif this set contains no elements.iterator()Returns an iterator over the elements in this set in ascending order.last()Returns the last (highest) element currently in this set.Returns the greatest element in this set strictly less than the given element, ornullif there is no such element.Retrieves and removes the first (lowest) element, or returnsnullif this set is empty (optional operation).pollLast()Retrieves and removes the last (highest) element, or returnsnullif this set is empty (optional operation).booleanRemoves the specified element from this set if it is present.booleanremoveAll(Collection<?> c) Removes from this set all of its elements that are contained in the specified collection.intsize()Returns the number of elements in this set.Returns aSpliteratorover the elements in this set.Returns a view of the portion of this set whose elements range fromfromElementtotoElement.Returns a view of the portion of this set whose elements range fromfromElement, inclusive, totoElement, exclusive.Returns a view of the portion of this set whose elements are greater than or equal tofromElement.Returns a view of the portion of this set whose elements are greater than (or equal to, ifinclusiveis true)fromElement.Methods declared in class java.util.AbstractSet
hashCodeMethods declared in class java.util.AbstractCollection
addAll, containsAll, retainAll, toArray, toArray, toStringMethods declared in interface java.util.Collection
parallelStream, removeIf, stream, toArrayMethods declared in interface java.util.NavigableSet
removeFirst, removeLast, reversed
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Constructor Details
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ConcurrentSkipListSet
public ConcurrentSkipListSet()Constructs a new, empty set that orders its elements according to their natural ordering. -
ConcurrentSkipListSet
Constructs a new, empty set that orders its elements according to the specified comparator.- Parameters:
comparator- the comparator that will be used to order this set. Ifnull, the natural ordering of the elements will be used.
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ConcurrentSkipListSet
Constructs a new set containing the elements in the specified collection, that orders its elements according to their natural ordering.- Parameters:
c- The elements that will comprise the new set- Throws:
ClassCastException- if the elements incare notComparable, or are not mutually comparableNullPointerException- if the specified collection or any of its elements are null
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ConcurrentSkipListSet
Constructs a new set containing the same elements and using the same ordering as the specified sorted set.- Parameters:
s- sorted set whose elements will comprise the new set- Throws:
NullPointerException- if the specified sorted set or any of its elements are null
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Method Details
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clone
Returns a shallow copy of thisConcurrentSkipListSetinstance. (The elements themselves are not cloned.) -
size
public int size()Returns the number of elements in this set. If this set contains more thanInteger.MAX_VALUEelements, it returnsInteger.MAX_VALUE.It is possible for the size to change during execution of this method, in which case the returned result will be inaccurate. Thus, this method is typically not very useful in concurrent applications.
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isEmpty
public boolean isEmpty()Returnstrueif this set contains no elements.- Specified by:
isEmptyin interfaceCollection<E>- Specified by:
isEmptyin interfaceSet<E>- Overrides:
isEmptyin classAbstractCollection<E>- Returns:
trueif this set contains no elements
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contains
Returnstrueif this set contains the specified element. More formally, returnstrueif and only if this set contains an elementesuch thato.equals(e).- Specified by:
containsin interfaceCollection<E>- Specified by:
containsin interfaceSet<E>- Overrides:
containsin classAbstractCollection<E>- Parameters:
o- object to be checked for containment in this set- Returns:
trueif this set contains the specified element- Throws:
ClassCastException- if the specified element cannot be compared with the elements currently in this setNullPointerException- if the specified element is null
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add
Adds the specified element to this set if it is not already present. More formally, adds the specified elementeto this set if the set contains no elemente2such thate.equals(e2). If this set already contains the element, the call leaves the set unchanged and returnsfalse.- Specified by:
addin interfaceCollection<E>- Specified by:
addin interfaceSet<E>- Overrides:
addin classAbstractCollection<E>- Parameters:
e- element to be added to this set- Returns:
trueif this set did not already contain the specified element- Throws:
ClassCastException- ifecannot be compared with the elements currently in this setNullPointerException- if the specified element is null
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remove
Removes the specified element from this set if it is present. More formally, removes an elementesuch thato.equals(e), if this set contains such an element. Returnstrueif this set contained the element (or equivalently, if this set changed as a result of the call). (This set will not contain the element once the call returns.)- Specified by:
removein interfaceCollection<E>- Specified by:
removein interfaceSet<E>- Overrides:
removein classAbstractCollection<E>- Parameters:
o- object to be removed from this set, if present- Returns:
trueif this set contained the specified element- Throws:
ClassCastException- ifocannot be compared with the elements currently in this setNullPointerException- if the specified element is null
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clear
public void clear()Removes all of the elements from this set.- Specified by:
clearin interfaceCollection<E>- Specified by:
clearin interfaceSet<E>- Overrides:
clearin classAbstractCollection<E>
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iterator
Returns an iterator over the elements in this set in ascending order.- Specified by:
iteratorin interfaceCollection<E>- Specified by:
iteratorin interfaceIterable<E>- Specified by:
iteratorin interfaceNavigableSet<E>- Specified by:
iteratorin interfaceSet<E>- Specified by:
iteratorin classAbstractCollection<E>- Returns:
- an iterator over the elements in this set in ascending order
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descendingIterator
Returns an iterator over the elements in this set in descending order.- Specified by:
descendingIteratorin interfaceNavigableSet<E>- Returns:
- an iterator over the elements in this set in descending order
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equals
Compares the specified object with this set for equality. Returnstrueif the specified object is also a set, the two sets have the same size, and every member of the specified set is contained in this set (or equivalently, every member of this set is contained in the specified set). This definition ensures that the equals method works properly across different implementations of the set interface.- Specified by:
equalsin interfaceCollection<E>- Specified by:
equalsin interfaceSet<E>- Overrides:
equalsin classAbstractSet<E>- Parameters:
o- the object to be compared for equality with this set- Returns:
trueif the specified object is equal to this set- See Also:
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removeAll
Removes from this set all of its elements that are contained in the specified collection. If the specified collection is also a set, this operation effectively modifies this set so that its value is the asymmetric set difference of the two sets.- Specified by:
removeAllin interfaceCollection<E>- Specified by:
removeAllin interfaceSet<E>- Overrides:
removeAllin classAbstractSet<E>- Parameters:
c- collection containing elements to be removed from this set- Returns:
trueif this set changed as a result of the call- Throws:
ClassCastException- if the class of an element of this set is incompatible with the specified collection (optional)NullPointerException- if the specified collection or any of its elements are null- See Also:
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lower
Description copied from interface:NavigableSetReturns the greatest element in this set strictly less than the given element, ornullif there is no such element.- Specified by:
lowerin interfaceNavigableSet<E>- Parameters:
e- the value to match- Returns:
- the greatest element less than
e, ornullif there is no such element - Throws:
ClassCastException- if the specified element cannot be compared with the elements currently in the setNullPointerException- if the specified element is null
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floor
Description copied from interface:NavigableSetReturns the greatest element in this set less than or equal to the given element, ornullif there is no such element.- Specified by:
floorin interfaceNavigableSet<E>- Parameters:
e- the value to match- Returns:
- the greatest element less than or equal to
e, ornullif there is no such element - Throws:
ClassCastException- if the specified element cannot be compared with the elements currently in the setNullPointerException- if the specified element is null
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ceiling
Description copied from interface:NavigableSetReturns the least element in this set greater than or equal to the given element, ornullif there is no such element.- Specified by:
ceilingin interfaceNavigableSet<E>- Parameters:
e- the value to match- Returns:
- the least element greater than or equal to
e, ornullif there is no such element - Throws:
ClassCastException- if the specified element cannot be compared with the elements currently in the setNullPointerException- if the specified element is null
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higher
Description copied from interface:NavigableSetReturns the least element in this set strictly greater than the given element, ornullif there is no such element.- Specified by:
higherin interfaceNavigableSet<E>- Parameters:
e- the value to match- Returns:
- the least element greater than
e, ornullif there is no such element - Throws:
ClassCastException- if the specified element cannot be compared with the elements currently in the setNullPointerException- if the specified element is null
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pollFirst
Description copied from interface:NavigableSetRetrieves and removes the first (lowest) element, or returnsnullif this set is empty (optional operation).- Specified by:
pollFirstin interfaceNavigableSet<E>- Returns:
- the first element, or
nullif this set is empty
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pollLast
Description copied from interface:NavigableSetRetrieves and removes the last (highest) element, or returnsnullif this set is empty (optional operation).- Specified by:
pollLastin interfaceNavigableSet<E>- Returns:
- the last element, or
nullif this set is empty
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comparator
Description copied from interface:SortedSetReturns the comparator used to order the elements in this set, ornullif this set uses the natural ordering of its elements.- Specified by:
comparatorin interfaceSortedSet<E>- Returns:
- the comparator used to order the elements in this set,
or
nullif this set uses the natural ordering of its elements
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first
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last
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addFirst
ThrowsUnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.- Specified by:
addFirstin interfaceSequencedCollection<E>- Specified by:
addFirstin interfaceSortedSet<E>- Parameters:
e- the element to be added- Throws:
UnsupportedOperationException- always- Since:
- 21
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addLast
ThrowsUnsupportedOperationException. The encounter order induced by this set's comparison method determines the position of elements, so explicit positioning is not supported.- Specified by:
addLastin interfaceSequencedCollection<E>- Specified by:
addLastin interfaceSortedSet<E>- Parameters:
e- the element to be added.- Throws:
UnsupportedOperationException- always- Since:
- 21
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subSet
public NavigableSet<E> subSet(E fromElement, boolean fromInclusive, E toElement, boolean toInclusive) Description copied from interface:NavigableSetReturns a view of the portion of this set whose elements range fromfromElementtotoElement. IffromElementandtoElementare equal, the returned set is empty unlessfromInclusiveandtoInclusiveare both true. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.The returned set will throw an
IllegalArgumentExceptionon an attempt to insert an element outside its range.- Specified by:
subSetin interfaceNavigableSet<E>- Parameters:
fromElement- low endpoint of the returned setfromInclusive-trueif the low endpoint is to be included in the returned viewtoElement- high endpoint of the returned settoInclusive-trueif the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements range from
fromElement, inclusive, totoElement, exclusive - Throws:
ClassCastException- iffromElementandtoElementcannot be compared to one another using this set's comparator (or, if the set has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception iffromElementortoElementcannot be compared to elements currently in the set.NullPointerException- iffromElementortoElementis nullIllegalArgumentException- iffromElementis greater thantoElement; or if this set itself has a restricted range, andfromElementortoElementlies outside the bounds of the range.
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headSet
Description copied from interface:NavigableSetReturns a view of the portion of this set whose elements are less than (or equal to, ifinclusiveis true)toElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.The returned set will throw an
IllegalArgumentExceptionon an attempt to insert an element outside its range.- Specified by:
headSetin interfaceNavigableSet<E>- Parameters:
toElement- high endpoint of the returned setinclusive-trueif the high endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements are less than
(or equal to, if
inclusiveis true)toElement - Throws:
ClassCastException- iftoElementis not compatible with this set's comparator (or, if the set has no comparator, iftoElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iftoElementcannot be compared to elements currently in the set.NullPointerException- iftoElementis nullIllegalArgumentException- if this set itself has a restricted range, andtoElementlies outside the bounds of the range
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tailSet
Description copied from interface:NavigableSetReturns a view of the portion of this set whose elements are greater than (or equal to, ifinclusiveis true)fromElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.The returned set will throw an
IllegalArgumentExceptionon an attempt to insert an element outside its range.- Specified by:
tailSetin interfaceNavigableSet<E>- Parameters:
fromElement- low endpoint of the returned setinclusive-trueif the low endpoint is to be included in the returned view- Returns:
- a view of the portion of this set whose elements are greater
than or equal to
fromElement - Throws:
ClassCastException- iffromElementis not compatible with this set's comparator (or, if the set has no comparator, iffromElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iffromElementcannot be compared to elements currently in the set.NullPointerException- iffromElementis nullIllegalArgumentException- if this set itself has a restricted range, andfromElementlies outside the bounds of the range
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subSet
Description copied from interface:NavigableSetReturns a view of the portion of this set whose elements range fromfromElement, inclusive, totoElement, exclusive. (IffromElementandtoElementare equal, the returned set is empty.) The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.The returned set will throw an
IllegalArgumentExceptionon an attempt to insert an element outside its range.Equivalent to
subSet(fromElement, true, toElement, false).- Specified by:
subSetin interfaceNavigableSet<E>- Specified by:
subSetin interfaceSortedSet<E>- Parameters:
fromElement- low endpoint (inclusive) of the returned settoElement- high endpoint (exclusive) of the returned set- Returns:
- a view of the portion of this set whose elements range from
fromElement, inclusive, totoElement, exclusive - Throws:
ClassCastException- iffromElementandtoElementcannot be compared to one another using this set's comparator (or, if the set has no comparator, using natural ordering). Implementations may, but are not required to, throw this exception iffromElementortoElementcannot be compared to elements currently in the set.NullPointerException- iffromElementortoElementis nullIllegalArgumentException- iffromElementis greater thantoElement; or if this set itself has a restricted range, andfromElementortoElementlies outside the bounds of the range
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headSet
Description copied from interface:NavigableSetReturns a view of the portion of this set whose elements are strictly less thantoElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.The returned set will throw an
IllegalArgumentExceptionon an attempt to insert an element outside its range.Equivalent to
headSet(toElement, false).- Specified by:
headSetin interfaceNavigableSet<E>- Specified by:
headSetin interfaceSortedSet<E>- Parameters:
toElement- high endpoint (exclusive) of the returned set- Returns:
- a view of the portion of this set whose elements are strictly
less than
toElement - Throws:
ClassCastException- iftoElementis not compatible with this set's comparator (or, if the set has no comparator, iftoElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iftoElementcannot be compared to elements currently in the set.NullPointerException- iftoElementis nullIllegalArgumentException- if this set itself has a restricted range, andtoElementlies outside the bounds of the range
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tailSet
Description copied from interface:NavigableSetReturns a view of the portion of this set whose elements are greater than or equal tofromElement. The returned set is backed by this set, so changes in the returned set are reflected in this set, and vice-versa. The returned set supports all optional set operations that this set supports.The returned set will throw an
IllegalArgumentExceptionon an attempt to insert an element outside its range.Equivalent to
tailSet(fromElement, true).- Specified by:
tailSetin interfaceNavigableSet<E>- Specified by:
tailSetin interfaceSortedSet<E>- Parameters:
fromElement- low endpoint (inclusive) of the returned set- Returns:
- a view of the portion of this set whose elements are greater
than or equal to
fromElement - Throws:
ClassCastException- iffromElementis not compatible with this set's comparator (or, if the set has no comparator, iffromElementdoes not implementComparable). Implementations may, but are not required to, throw this exception iffromElementcannot be compared to elements currently in the set.NullPointerException- iffromElementis nullIllegalArgumentException- if this set itself has a restricted range, andfromElementlies outside the bounds of the range
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descendingSet
Returns a reverse order view of the elements contained in this set. The descending set is backed by this set, so changes to the set are reflected in the descending set, and vice-versa.The returned set has an ordering equivalent to
Collections.reverseOrder(comparator()). The expressions.descendingSet().descendingSet()returns a view ofsessentially equivalent tos.- Specified by:
descendingSetin interfaceNavigableSet<E>- Returns:
- a reverse order view of this set
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spliterator
Returns aSpliteratorover the elements in this set.The
SpliteratorreportsSpliterator.CONCURRENT,Spliterator.NONNULL,Spliterator.DISTINCT,Spliterator.SORTEDandSpliterator.ORDERED, with an encounter order that is ascending order. Overriding implementations should document the reporting of additional characteristic values.The spliterator's comparator is
nullif the set's comparator isnull. Otherwise, the spliterator's comparator is the same as or imposes the same total ordering as the set's comparator.- Specified by:
spliteratorin interfaceCollection<E>- Specified by:
spliteratorin interfaceIterable<E>- Specified by:
spliteratorin interfaceSet<E>- Specified by:
spliteratorin interfaceSortedSet<E>- Returns:
- a
Spliteratorover the elements in this set - Since:
- 1.8
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